Wired or wireless: Which is the best technology for sensor deployment?

Some would even argue that defining the points to be measured was the starting point from which systems were defined, and ultimately dictated what the deployed systems could and could not do.

This is no less true as IoT technologies are adopted in the transition to Industry 4.0. In fact, the adoption of these new technologies increases the demand for more and more measurement data, as users include an ever-increasing number of factors into the optimisation of their processes
and equipment.

This hunger to add new data brings its own challenges and some significant differences. The inherent flexibility of IoT systems means that the required data measurements evolve over time, requiring strategies to integrate pre-existing measurement points with new ones, which can often be physically removed from any pre-existing wiring or communication links.

In such cases, the cost of adding the new measurement points – or, more normally, the cost of recovering the data from these points –
can often be the deciding factor in whether a desired system enhancement will make economic sense. It is therefore understandable that engineers are interested in the deployment of wireless measurement systems, as these can often be installed much more quickly and cost effectively than those involving the laying and routing of additional wired infrastructure. Deploying wireless sensing technology involves compromises, however, and it is the effect of these compromises that ultimately determines if a wired or wireless architecture is selected
and, if the latter, which radio technology is most suitable.

The case for wired infrastructure

The traditional way sensors have been connected to data acquisition systems is via wired interfaces, typically 4-20mA current loops, but also, in the case of more specialised measurements, via higher speed voltage-based systems. These connections can carry power to the sensors, are reliable, accurate, and offer faster measurement transmission and update times than wireless systems. Furthermore, if correctly installed, they are both highly secure
and insensitive to noise and other interference. These characteristics come at a cost, however. The cost of installation can be very high, often involving alterations to buildings or digging trenches in which to lay the cables. In some cases, cabling to a sensor that is geographically remote may not be physically practical. It is also usually not possible to use wired interfaces to mobile equipment, unless the range of movement is limited and can be accurately forecasted.

Read the full article in the April issue of DPA